With the recent development of information communication technology, a variety of wireless communication techniques are being developed. From among them, a Wireless Local Area Network (WLAN) is a technique for wirelessly accessing the Internet at homes or companies or in specific service providing areas by using portable terminals, such as a Personal Digital Assistant (PDA), a laptop computer, and a Portable Multimedia Player (PMP), based on wireless frequency technology.
A lot of standardization tasks are being performed since Institute of Electrical and Electronics Engineering (IEEE) 802 (i.e., the standardization organization of WLAN technology) was established on February, 1980.
WLAN technology initially supported a speed of 1 to 2 Mbps through frequency hopping, band spreading, and infrared communication by using a frequency of 2.4 GHz according to IEEE 802.11, but recently may support a maximum speed of 54 Mbps by using Orthogonal Frequency Division Multiplexing (OFDM). In addition, in IEEE 802.11, standardizations for various techniques, such as the improvement of Quality of Service (QoS), Access Point (AP) protocol compatibility, security enhancement, radio resource measurement, wireless access vehicular environments, fast roaming, a mesh network, interworking with an external network, and wireless network management, are being put to practical use or developed.
Furthermore, in order to overcome a limit to the communication speed that was considered as being weakness in the WLAN, IEEE 802.11n has recently been established as a technical standard. An object of IEEE 802.11n is to increase the speed and reliability of a network and to extend the coverage of a wireless network. More particularly, in order to support a High Throughput (HT) having a maximum data processing speed of 540 Mbps or higher, minimize an error in transmission, and optimize the data speed, IEEE 802.11n is based on Multiple Inputs and Multiple Outputs (MIMO) technology using multiple antennas on both sides of a transmitter and a receiver. For a necessity for high quality and broadband data transmission according to increased users and in order to reduce transmit power, use radio resources efficiently, and extend the service coverage, the IEEE 802.11n standard supports beamforming technology and data transmission through a maximum of four spatial streams. Furthermore, this standard may use not only a coding scheme for transmitting several redundant copies in order to increase data reliability, but also Orthogonal Frequency Division Multiplex (OFDM) in order to increase the speed.
As the WLAN is actively propagated and applications employing the WLAN are diversified, WLAN service coverage is increasing. As hotspots providing WLAN service increases, an Overlapping Basic Service Set (OBSS) environment in which all or part of Basic Service Areas (BSA), that is, the service coverages of the hotspots overlap with each other is increasing. A station operating in the OBSS environment is influenced by a neighboring Basic Service Set (BSS) that forms the OBSS. Reliability of data transmission and the throughput of a WLAN system may be deteriorated because the transmission/reception of data in the neighboring BSS acts as interference. Accordingly, in data transmission/reception between STAs including an AP operating in an OBSS environment, a transmission/reception method for minimizing mutual interference and a protocol for the transmission/reception method need to be taken into consideration.